Geomagnetic Storms:Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm

Updated at: 2011 Jul 26 2200 UTC

Mid-latitudes

0-24 hr

24-48 hr

ACTIVE

05 %

15 %

MINOR

01 %

05 %

SEVERE

01 %

01 %

High latitudes

0-24 hr

24-48 hr

ACTIVE

05 %

15 %

MINOR

01 %

10 %

SEVERE

01 %

01 %

Tuesday, Jul. 26, 2011

What's up in space

Metallic photos of the sun by renowned photographer Greg Piepol bring together the best of art and science. Buy one or a whole set. They make a stellar gift.

SPACESHIP AT DAWN: The International Space Station is beginning a series of bright morning passes over North America. Check the Simple Satellite Tracker for flyby times, then set your alarm to see a spaceship at dawn. It's a nice way to start the day.

"I went outside to see the Moon and Pleiades after midnight on July 25th when the auroras appeared," says Johnson. "It was beautiful."

More auroras are possible tonight as the solar wind continues to blow faster than ~500 km/s. Conditions favor observers in the southern hemisphere where skies are winter-dark. Aurora alerts:text, voice.

NOCTILUCENT CLOUDS: "The morning of July 26th was electric blue!" says Heiko Ulbricht of Freital, Saxony, Germany. "I woke up at 3 clock, looked out my bedroom window to the north and saw a stunning display of noctilucent clouds." Moments later, he dashed outside with a camera to record the view:

July has been an odd time for noctilucent clouds (NLCs). The month began with an extravagant display that stretched as far south as Colorado and Kansas--odd because NLCs are usually confined to higher latitudes. The event seemed to herald a period of widespread sightings. Observers were disappointed, though, when the clouds quickly retreated to their usual northern habitat. Could this German apparition signal renewed activity? Sky watchers at all latitudes should be alert for electric-blue ripples around sunrise and sunset. Observing tips may be found in the gallery.

Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.